I’m looking forward to more discussions and replies by @GoldenSound and @ADU , great learning opportunity for me because I’m still confused about the what @ADU pointed out in these videos, what Free Field means for headphones (people including me are mostly negative about the Grell OAE1 which attempts to mimic FF?), and what neutral means for headphones at all. Sean Olive said in one of the videos that people actually DON’T prefer Diffuse Field sounds, or was he talking about how it’s not a realistic sound that people prefer over speakers in a mildly echoey room? To me Harman curve is mostly just Diffused Field + bass with some small deviations by like a few db here and there?
Alright those are my confusions, looking forward to hearing further discussions to clear things up!
It is something we have considered however it requires breaking the seal on any sealed unit we sell and makes things more complicated if people feel like they are getting open-box pair of headphones when it’s a new sealed unit. Also makes it harder on our end from a customer service perspective.
As far as offering a service to have headphones sent in, it’s a similar situation. Each one of us at Headphones.com have quite a few things on our plate at any one time so offering a headphone measuring service would pretty much require a new, full-time employee while also making sure that it did not interrupt the flow of content for any of our creators. Along with dealing with shipping issues, gear breaking, etc…
That’s not to say that neither of those things are possible. They just aren’t something we currently have the bandwidth to offer.
It’s not that people don’t prefer DF condition, it’s that people don’t prefer a raw DF response… in the same way that people prefer a downward tilt from bass to treble in speakers.
So using DF as a baseline and applying the preference filters (bass and treble shelves) is perfectly practical, and also what Sean’s been doing in his more recent research.
You could also apply other filters, like the way Crinacle does, where he has tilt + boost. There are many ways to achieve the bass to treble delta that people prefer… Harman is just one of them.
I understand. And thanks for taking the time to weigh in on this, Taron. Maybe I can get to a CanJam some time, and try to get a few squigs done there.
I’ve also considered trying to rent a good HATS to do my own measurements. Not sure how practical or doable that would be though.
I had one other general housekeeping question on this. We already have a place to request reviews and measurements of headphones here…
I was just wondering though if there was somethin comparable for source components (ie amps, DACs, players, etc.). Or if I should also post my requests on that in the above topic?
Yup that would be the best place for all review requests! You’ll find that @GoldenSound is really the only one that will review source gear though outside of the odd video from DMS so it is a bit harder for a suggestion to be pulled when only 1 or 2 videos are made a month in comparison to the headphone reviews.
As @taronlissimore mentioned it’s mostly myself that covers source gear. I’m always keen for input on what people want to see covered. But a lot of the time it’s just a case of what’s practical.
Some companies actually don’t want to send stuff, often cause they know it’ll be measured and they want to avoid that. So I can’t review it unless I can borrow a unit from a friend.
Some companies will send stuff but it takes a long time to get it, (I’ve been trying to get ahold of the iFi Phantom for a year and the Topping Centaurus I won’t be able to get until at least the end of the month).
And sometimes it’s just a case of stuff not really being interesting enough to cover, which is why I don’t typically review the regularly released ESS/AKM based DACs etc that don’t really have anything new over the one released last month.
So usually the stuff getting covered is basically down to:
Is it interesting/something worth covering
Can a unit actually be gotten in for review (and within a reasonable time frame, it’s less ideal to review something if there are other reviewers publishing stuff on it but I can’t get ahold of one until months later).
But if there are particular products you’d like to see covered please do post in that thread as it does factor into what gets picked!
Fwiw, I’d like to hear some more of Cam’s and other folks thoughts on this as well. And didn’t really mean to scare anyone away with the above videos.
There are alot of questions and confusion around these topics though, Luke. Even among the experts. And I recall Dr. Olive lamenting in another recent video the recent resurgence of interest in things like diffuse fields for probably precisely this reason, I believe. I’m probably partly responsible for that resurgence though. Because how we analyze, display, and use measurements has been a subject of some interest to me for quite awhile. Probably since the inception of the Harman headphone studies in 2012-2013, or even before that. And I think DF has its place in those conversations.
I understand where Sean is coming from on this though. Because when he came on the scene, and started looking at the sound quality of headphones, diffuse field was really the only game in town. And there wasn’t much other practical science to help guide developers, reviewers, and users in a specific direction. There was plenty of opinion on this though. Just like there is now.
I don’t know all of the exact history on this, but I think Paul Barton (of PSB and NAD) was probably the first to really specify a connection between the in-ear response of speakers in a room, and FR in headphones. His term for this was “RoomFeel ™”. And it was a natural idea for him, since he started out designing, building, and selling speakers before getting involved in the development of headphones. Tyll Hertsens of HeadRoom and Inner Fidelity was another early advocate for this, and one of the principal supporters and disseminators of the Harman research on this topic.
Many headphone developers were already ahead of the game though on this. And very few actually followed the diffuse field standard, from the beginning. So the Harman research really only helped to cement and cotify alot of opinions and viewpoints that were already progressing in some similar directions.
Where that leaves us now is really just arguing over alot of the details in the research, and what’s actually important in it. I think most of us here probably agree on more than 80% of what gets discussed on this. So it’s just the remaining 5,10, 15 or 20% where we’re having some trouble building a consensus. I applaud the efforts of Headphones.com in trying to better square the measurements with people’s perceptions, for example. Even though I don’t necessarily agree with all the choices that are being made on this. And sometimes feel the forest is being lost for all the trees, as I think Sean sometimes does.
I also don’t agree with Sean on everything, including some of his takes on the K371. And I don’t think the current Harman GRAS target is a perfect model for rating/assessing the in-ear response of headphones, even though it’s rooted in some pretty good science on preference and measurements. My principal takeaways from the Harman studies are the same as what he is stating in the three videos above though. Namely, that things like preference, and fidelity, and neutrality are very closely linked. And most people, a majority, prefer headphones that measure pretty close to the in-ear response of neutral loudspeakers in a semi-reflective room.
When Sean Olive talks about a “neutral sound” in a pair headphones, I believe this is what he means. He means that it measures and sounds comparable to a pair of neutral loudspeakers in terms of frequency response. For more on that subject you can look at Floyd Toole’s CIRMMT video, which explains what neutral is in a loudspeaker (measured in a room, rather than inside the ear at the DRP or ear drum reference point) in some fairly good detail.
I know this doesn’t answer all of your questions on diffuse and free fields. There’s quite a bit more ground to cover on that though. And we have to start somewhere.
You can listen to what a diffuse and free field sound like on pair of headphones btw. If you already own a pair of neutral headphones, you can simply add a 10 to 15 dB tilt to their response toward the treble, and that should get you fairly close, depending somewhat on the brightness or darkness of the headphone. You can also use a program like EAPO’s Configuration Editor to do a more precise simulation based on the measurements of your headphones and a diffuse field for the same rig. I prefer to use HBK 5128 headphone measurements, and HBK’s original 1/3-octave 5128 DF measurement for this. I think that their DF measurement is only good up to about 16 kHz though. And above that, it probably overestimates the in-ear response of DF to a pretty significant degree, due to a lack of resolution in that high frequency range.
Keep your volume low when trying this, because DF has significantly more treble and energy in the higher frequencies than you’re probably used to, or should normally be listening to.
I will! Though I’m not sure they’ll be that interesting. The two components I’m probably most interested in at the moment are made by Bellari/Rolls. I think it’s probably about time to maybe consider a new DAC though as well. And not sure where to get started on that.
My question is if this sounds closer to Free Field than Diffused field, and we still need to add a fairly large bass shelf regardless for headphones to sound right?
From what you’re quoting it sounds more like it’s “Free field + bass shelf” = ideal, whereas others are saying “Diffuse field + bass shelf” = ideal. And neither make any claims to be more accurate, merely more neutral and preferred, is that correct?
Hehe I have a set of Grell OAE1, specifically tuned to sound like speakers at 30 degrees out. I think I get the idea.
What is it that you don’t agree with? I just bought a set of them for a test and listen with and without EQ. I found them quite alright. my gripes with it is more with the build quality, channel matching (left leaks to the right quite a lot on my unit), and ergonomics. The sound itself is decent, and with my custom EQ it sounds almost as good as any other headphones out there, cementing my experience and stance that frequency response is 80% or more of my preference for headphones, and that I could get pretty much my ideal frequency response via EQ with any headphones without noticeable physical limitations on the extreme ends of the FR.
I 'm not up on all the latest meta target curves other people are using. So can’t really comment on this intelligently. And it isn’t something that is really addressed directly in any of the previous Harman research. In a nutshell, the Harman research says free and diiffuse field = bad. In-ear response of neutral speakers in a semi-reflective room = good.
I use DF + a sound power slope in the -1.0 to -1.5 dB per octave range to roughly approximate the in-ear response of speakers. If you subtract HBK’s 1/3-octave 5128 DF from the 5128 FR measurements of headphones that approximate the Harman 2018 over-ear target on a GRAS rig, you’ll end up in that general ballpark. So I think it’s also a pretty good simulation of the Harman target response, albeit with a little more air/treble. Imo this is a pretty good reference up to about 16 kHz. Above that, HBK’s DF is too bright, and shouldn’t be followed, even with the SP slope added.
I don’t use the current Headphones.com DF curves for this btw, because they have a different response in the mid treble. And I also don’t use the current pref curves, even though they may get you somewhat close to same type of response.
I believe some actual in-ear measurements of speakers would help us to make better determinations though on all of the above. And that’s why I continue to encourage graphers to go more in that direction.
So you’re using measurement results to make your own EQ profiles? For some reason I thought you were making them while comparing to flat speakers in your room.
Anyway, you prefer this DF + slope because of personal enjoyment preference, or that it’s ideologically “neutral” and correct, or something else?
Isn’t that what Free Field curve on headphones are? And circling back to that, isn’t this demonstrably less preferred than Diffuse Field, and even less than Diffuse Field + bass shelf? Thought this was settled decades ago, but I guess I must be missing something important, wouldn’t be the first time haha.
Even though the K371 was designed to match the Harman 2018 over-ear target, there are other headphones that get a little closer to that. It might be a little closer to one of Harman’s bass-boosted variants though.
I don’t think the current Harman target is compeletely neutral though. So even if it did match the 2018 OE target perfectly, it would still probably sound a bit off to me.
I think headphones that measure close to the DF+SP model I described above will sound neutral. Until we have some in-ear measurements for comparison though, it is just my opinion. And I am open to being proved wrong on this.
This is something I’ve tried in the past. But not something I’m doing currently. I am in the process of acquiring some new neutral speakers though, for both pleasure listening and also more critical listening and evaluations. Comparing their in situ sound to headphones would likely also be part of that process.
I use the DF+SP model as my reference point for EQ and FR assessments because it closely matches the measurements of headphones with a reputation for a neutral response. And also matches the response of headphones tuned close to the Harman target across most of the audible frequency range. They will also fall pretty squarely within the -1.0 to -1.5 dB/octave slope range that I described above (after compensation with HBK’s 1/3-octave 5128 DF curve). And also because it sounds neutral to my ears.
So it is “ideologically correct” (to use your term) in that it conforms pretty closely to the Harman research results. And I also like the results, and think they sound good. So it’s also correct for me on a subjective level. I feel like I’m getting most of the timbral/tonal info I want from the music. It varies to some degree though, based on the recording.
To answer the question above simply, no, the in-ear response of speakers in a semi-reflective room would not be the same as a free field response curve, or a diffuse field curve.
Free field measurements are normally done in a heavily treated, echo-free room or enclosure. IOW, a room or sound field that’s free of any reflected sounds. So all you’re getting is the pure tone of the speaker or tone generator from a single direction, without the interference of any other reflected sounds from the room.
Diffuse field measurements, on the other hand, are done in reverberant rooms where the sound is coming more or less equally from all directions.
The direction of a free field sound source can also be varied relative to the measurement rig. So you can measure a dummy head’s response to a tone that originates directly in front of it, or behind it, or to the side, or even from above its head.
When you do measurements like this with a dummy head & torso simulator (HATS) in either an anechoic or diffuse room, what you’re actually measuring is the response or effect of the rig’s physical anatomy (ie its head, torso, and ears) to either a spectrally flat point source (free field) or spectrally flat diffuse sound field. IOW, the energy is usually equal at all frequencies in these two types of free and diffuse field sources. These measurements are done with a mic located at the ear drum reference point (DRP), inside the HATS rig’s artifical ears and ear canal. And the measurements are also known as the rig’s diffuse or free field head-related transfer function, or HRTF for short.
You can measure the HATS rig’s response to other kinds of sound sources as well. For example, you could set one up in your own home, and measure its response to a pair of speakers at the place where you normally sit and listen to your music. This is the type of sound field that I and Sean Olive (and others) are referring to when we talk about the in-ear response of neutral speakers in a semi-reflective room.
The rooms in your home are neither perfect reflectors, nor perfect absorbers of sound. So, semi-reflective. And the speakers that you use don’t just radiate sound in a single direction. The sound goes in all directions, but not equally so, and what you hear is a mixture of the speakers’ direct, reflected, and diffused sound in the room.
This also effects the spectral balance of sound, because most speakers tend to radiate more broadly in the lower frequencies. So even if your speakers measure flat across all frequencies from directly in front in a free field, when you put them in a semi-reflective space like the rooms in your home, the sound that you hear becomes tilted more towards the lower frequencies due to the attenuation of higher frequencies in the reflected and diffuse sounds.
The Harman over-ear target and earlier Olive-Welti curve are both rough approximations of the in-ear steady-state response of speakers in a semi-reflective space similar to your home, measured at the sweet spot or listening position (LP) in the room using different measurement rigs.
Here’s a photo of Tyll Hertsen’s Head Acoustics rig being used to measure the in-ear response of some speakers in Harman’s reference listening room btw. This was kindly posted on ASR a couple years ago by NTK.
This is probably neither here nor there. But since you asked, Luke, I’ll also mention another reason I like the DF+SP model better than some other models or ideas proposed here and elsewhere. The DF+SP model allows me to incorporate both the good and, if I choose, also some of the maybe not so good aspects of neutral speakers into my modeling of an in-ear response, via some more recent measurement data on both speakers and headphones.
If I don’t like the sound of HBK’s 1/3-octave 5128 DF with just a slope or bass boost, for example, then I have the option to look at some of the other recent sound power data on loudspeakers, and to incorporate some other things I might find there that might give better results with the content I listen to… such as a dip at 2k, or maybe a little boost at around 6k, or perhaps a little more rolloff in the sub-bass. As I described here and here, justifications for that sort of thing can often be found within the recent measurement data on speakers.
So the DF+SP model allows me to move a bit beyond the general confines of Harman’s old 3-knob preferred in-room response curve and the GRAS fixture measurements, and to experiment with some other useful and potentially better-sounding variations on the Harman theme, without straying too far away from either the general spirit or the letter of the Harman conclusions.